This invention relates to the field of radio frequency receivers and transmitters operating without disruptive signal interference in close physical proximity while located for example in an aircraft or other vehicle.
The conventional present day technique for providing continuous wave signal interference mitigation between a co-located or common platform radio frequency transmitter and receiver, in an aircraft setting for example, involves installing signal couplers in the transmission path between the transmitter and the transmitting antenna. Such couplers obtain a copy of a receiver-interfering strong transmitter signal for use in a signal subtraction or cancellation arrangement. This technique is represented generally in the FIG. 8 drawing herein. The copied strong transmitter signal is then provided with the proper phase and amplitude characteristics and coupled into the signal path between the receiving antenna and the receiver to achieve cancellation of the offending signal. Using this technique a significant amount of host platform, or e.g. host aircraft, characterization must be performed to install the signal suppression architectures. Common platforms requiring suppression of multiple offending transmitter signals in multiple receiver signal lines, will benefit from a better approach to interference mitigation.
The present invention provides active interference signal cancellation protection for a low level receiver operating near a transmitter antenna and provides this protection with a nonlinear ferrite element and without need to access a sample of the transmitter signal at its source.
It is an object of the present invention therefore to protect a radio receiver apparatus operating in the vicinity of a radio transmitter from transmitter-sourced interference signals.
It is another object of the invention to provide radio receiver protection from adjacent transmitter interference without requiring direct access to a transmitter signal.
It is another object of the invention to provide radio receiver protection from adjacent transmitter interference through use of receiver antenna-collected signals.
It is another object of the invention to provide radio receiver protection from adjacent transmitter interference by way of an adaptive signal cancellation-based signal processing algorithm.
It is another object of the invention to provide radio receiver protection from adjacent transmitter interference by way of introducing a frequency selective amplitude-sensitive nonlinear ferrite element into the generation of a transmitter interference-cancellation signal.
It is another object of the invention to provide radio receiver protection from adjacent transmitter interference by way of introducing an amplitude and frequency responsive nonlinear ferrite element such as yttrium iron garnet into the generation of a transmitter interference-cancellation signal.
It is another object of the invention to provide radio receiver protection from adjacent transmitter interference by way of introducing an amplitude and frequency responsive yttrium iron garnet ferrite element disposed in one of film form and spherical form into the generation of a transmitter interference-cancellation signal.
It is another object of the invention to provide radio receiver protection from adjacent transmitter interference in a manner providing low received signal loss.
It is another object of the invention to provide a system of radio receiver protection from adjacent transmitter interference usable in a co-located platform environment such as in a military aircraft.
It is another object of the invention to provide radio receiver protection from adjacent continuous wave, pulsed or frequency hopped transmitter interference.
It is another object of the invention to provide adaptive cancellation-based radio receiver protection from adjacent continuous wave, pulsed or frequency hopped transmitter interference.
It is another object of the invention to provide a radio receiver protection from adjacent transmitter interference arrangement usable over a frequency range such as 50 megahertz to 18 gigahertz.
It is another object of the invention to provide active mode low signal loss radio receiver protection from adjacent transmitter interference.
It is another object of the invention to provide an active interference cancellation algorithm for use with continuous wave transmitter interference signals.
Additional objects and features of the invention will be understood from the following description and claims and the accompanying drawings.
These and other objects of the invention are achieved by the method of receiving a weaker desired radio frequency signal in the presence of a nearby transmitter-sourced adjacent frequency strong interference signal, said method comprising the steps of:
generating a first electrical signal having both said weaker desired radio frequency signal and said nearby transmitter-sourced adjacent frequency strong interference signal as components thereof;
forming, in a first electrical signal-connected first path apparatus, a second electrical signal in which said weaker desired radio frequency signal component is attenuated with respect to said nearby transmitter-sourced adjacent frequency strong interference signal component;
subtracting, in a first electrical signal-connected second path apparatus, said second electrical signal from said first electrical signal to form a third electrical signal of suppressed nearby transmitter-sourced adjacent frequency strong interference signal content and substantially unaltered weaker desired radio frequency signal content;
applying said third electrical signal of suppressed nearby transmitter-sourced adjacent frequency strong interference signal content and substantially unaltered weaker desired radio frequency signal content to an input port of a radio receiver apparatus.